Besides spectacle lenses, contact lenses are the next most popular vision correction device. Soft contact lenses become more popular than hard lenses due to the fact that they are more comfortable to wear, and easier to adapt to than the hard lenses, or as they are called “Rigid Gas Permeable” (RGP) lenses. One draw back of the soft lens is that the quality of vision is not as good as that provided by the hard lens, and it tends to deteriorate to less quality over time. Soft contact lens wearers compromise their visual quality for comfort.
Hard contact lenses have good structural integrality. The optical surface is well preserved throughout the wearing period. The visual acuity of a hard or rigid lens is good, when it is fitted properly; they provide crisp vision comparable to that of wearing eyeglasses. However, hard contact lenses have two big drawbacks: it is uncomfortable to wear, and hard to adapt to. It can take a new user of hard contacts up to 3-4 weeks to adapt, and to tolerate them. No hard contact lens are supposed to be used for continuous wear, i.e. wearing them to sleep in overnight. The lenses have to be removed before sleep, and soaked in disinfecting solution. Wearers of rigid lenses have to tolerate the regiments, the inconvenience and discomfort.
Therefore, it is desirable to provide a contact lens that is comfortable to wear, easy to adapt to, and provides high visual acuity vision. More desirably, a contact lens that can be wore continuously overnight and only needs to be disposed off or cleaned once a month or even longer.